1. Field of the Invention
This invention relates to an improved process for molding polyisocyanate based polymers and is more particularly concerned with improving the mold release properties of said polymers through the use of particular internal release agents.
2. Description of the Prior Art
The molding of polyisocyanate based articles both cellular and non-cellular, in a variety of shapes and using an assortment of polymer compositions and mold materials, is well known in the art. To prevent the molded pieces from sticking to the mold surfaces, mold release agents are generally employed. These agents can be in the form of external or internal release agents and it is this latter category which is preferred and which has been receiving a good deal of attention of late.
One class of internal release agents which has been found to be useful and is commercially available is the polysiloxane polymers having pendant carboxylic acid groups present along the polysiloxane backbone. Reference to such carboxy functional polysiloxanes can be found in U.S. Pat. Nos. 4,076,695, 4,220,727 and 4,379,100, and new product information bulletin "Dow Corning.RTM.Q2-7119 Fluid for RIM Internal Release" (Dow Corning Corp., Midland, Mich.).
We have now discovered a novel class of derivatives of the aforesaid carboxy functional polysiloxanes which are possessed of highly unexpected properties to be discussed below and which impart outstanding release properties to molded polyisocyanate polymers.